Thin film libraries of sputtered SixM1-x (M = Cr + Ni, Fe, Mn) have been investigated for use as negative electrode materials in Li-ion rechargeable batteries. Results from over 200 compositions are reported here. The observed capacity decreases as transition metal content increases, approaching zero around 50 atom % Si, and can be approximated assuming active Si in an inactive SiM (M = Cr, Fe, Mn or Ni) matrix. Plots of differential capacity vs. potential are characteristic of a-Si in an inert matrix, in agreement with X-ray diffraction results. The behavior of Si-Mn thin film libraries differs from that of Si-Fe and Si-Cr-Ni libraries for the range of 50 to 70 atom % Si. (C) 2005 The Electrochemical Society.